linux-kernel - Re: [ibm-acpi-devel] [PATCH 0/4] power: supply: add charge_behaviour property (force-discharge, inhibit-charge)

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Date:   Thu, 25 Nov 2021 11:04:32 -0700
From:   Kevin Locke <kevin@...inlocke.name>
To:     Thomas Weißschuh <linux@...ssschuh.net>
Cc:     linux-pm@...r.kernel.org, ibm-acpi-devel@...ts.sourceforge.net,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [ibm-acpi-devel] [PATCH 0/4] power: supply: add charge_behaviour
 property (force-discharge, inhibit-charge)

On Wed, 2021-11-24 at 00:27 +0100, Thomas Weißschuh wrote:
> this series adds support for the charge_behaviour property to the power
> subsystem and thinkpad_acpi driver.

Wonderful!  Thanks for working on this.

I can confirm inhibit-charge and force-discharge states work with
patch v2 on v5.16-rc2 on a T430 (2342-CTO) with BIOS G1ETC2WW (2.82 ),
EC G1HT36WW and a single battery.  Most behavior is as expected:

- With force-discharge, status becomes "Discharging" and energy_now
  drops over time while AC remains connected.
- With inhibit-charge, status becomes "Unknown" and energy_now is
  stable over time, even when not fully charged.
- With auto, status becomes "Charging" and energy_now rises over time.
- charge_behaviour takes precedence over
  charge_control_{start,end}_threshold: status remains
  Discharging/Unknown when below the start threshold, either due to
  discharge or threshold change.
- charge_behaviour is preserved over soft reboot.
- inhibit-charge/auto are preserved across battery removal and
  reinsertion.
- inhibit-charge/auto are preserved across s2ram (S3).
- With force-discharge, if the battery is removed, the machine
  immediately powers off.

Some behavior is a little surprising:

- charge_behaviour can not be set to force-discharge if AC is
  disconnected (EIO).  If charge_behaviour is force-discharge when AC
  is disconnected, it changes to auto, unlike inhibit-charge.
- charge_behavior force-discharge is not preserved across s2ram (S3),
  unlike inhibit-charge.
- charge_behaviour is not preserved across hard reset (unlike charge
  thresholds).  Interestingly, it appears that inhibit-charge is
  preserved across power-off (no charging is observed while powered
  off) but not power-on, even though it is preserved across soft
  reboot, as noted above.

I assume the behavior is under the control of the EC, so these aren't
criticisms of the patch.  Just some observations.

Tested-by: Kevin Locke <kevin@...inlocke.name>

Thanks again,
Kevin